Chemical Bonding

• Chemical bonding occurs as electrons are rearranged creating a substance with new physical and chemical properties– The changes cannot be physically altered or reversed– Can be reversed or changed chemically

Ionic Bonding• Ionic bonds are formed from the transfer of electrons from one atom to

another. The Ionic bond that forms is the result of the attraction of oppositely charged ions (atoms). The electrostatic attraction acts much like the opposite poles of a magnet. Here are some simple rules for ion formation and naming. – Ionic compounds consist of entirely ionic bonds (oppositely charged ions) – The ionic compound is electronically neutral (positive charges = negative charges) – Ions and ionic compounds are frequently more stable than their parent atoms – ionic compounds are made from a metal and a nonmetal

Criss-Cross• Charge on the ion becomes the subscript of the adjacent ion (1 is

not written)• The overall charge of the compound MUST be zero• Reduce subscripts to whole numbers if possible• Use parenthesis to group polyatomic ions

Covalent Bonding• A covalent bond is one where the electrons are shared. A group of

covalently bonded atoms is called a molecule. These molecular substances include DNA, sugar and carbon dioxide. The molecules can contain as few as 2 atoms and as many as a million. Rules for covalent bonds:– electrons are shared in covalent molecules – covalently bonded molecules follow the octet rule (some exceptions - BF3) – covalent molecules can form single, double, or triple bonds – covalent bonds can be rearranged to form different molecules (glucose,

fructose, & maltose)

Molecules and Compounds• Molecules are made entirely of non-metals forming covalent bonds

– Can have an overall charge and be classified as an ion (SO42-)

• Compounds are made entirely of oppositely charged ions– Dissolve in water to form electrolytes

• Elements, molecules, and compounds are considered pure substances as they cannot be physically altered and contain atoms in fixed ratios

• Mixtures are groups of elements, compounds, and/or molecules physically combined– Can be physically separated and are not considered pure– Can be combined using van der Waals forces … attraction by virtue of

overall charge or electron arrangement.• Weaker than covalent or ionic bonding